Firearm bolt assembly for a self-loading firearm

ABSTRACT

A firearm bolt assembly for a self-loading firearm has an elongated frame defining a frame axis, a bolt connected to a forward end of the frame, a plurality of separate weights connected to the frame, and the weights being movable at least slightly with respect to the frame and to each other for movement along the axis. There may be a resilient spacer element between adjacent weights. There may be a resilient spacer element between one of the weights and a portion of the frame. The spacer element may be an O-ring. The weights may be connected to a rear portion of the frame. The weights may be tubular bodies each defining a bore. A portion of the frame may be received within the bore. The frame may define a rear portion having a first diameter, and a flange forward of the rear portion having a larger second diameter.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of U.S. patent application Ser. No.14/958,840 filed on Dec. 3, 2015, entitled “FIREARM BOLT ASSEMBLY FOR ASELF-LOADING FIREARM,” which is hereby incorporated by reference in itsentirety for all that is taught and disclosed therein.

FIELD OF THE INVENTION

The present invention relates to firearms, and more particularly tofirearm bolt assemblies for self-loading rifles.

BACKGROUND OF THE INVENTION

Many self-loading rifles with a rotating-lock bolt use direct gasimpingement as their mechanism of operation. Gas is trapped from thebarrel as the bullet moves past a gas port located above the rifle'sfront sight base. The gas rushes into the port and down a gas tube,located above the barrel, which runs from the front sight base into therifle's upper receiver. Here, the gas tube protrudes into a “gas key”(bolt carrier key), which accepts the gas and funnels it into the boltcarrier.

The bolt and bolt carrier together effectively form a piston, which iscaused to move as the cavity in the bolt carrier fills with highpressure gas. The bolt is locked into the barrel extension, so thisexpansion forces the bolt carrier backward a short distance in line withthe stock of the rifle to first unlock the bolt. As the bolt carriermoves toward the butt of the gun, the bolt cam pin, riding in a slot onthe bolt carrier, forces the bolt to turn and unlock from the barrelextension. Once the bolt is fully unlocked it begins its rearwardmovement along with the bolt carrier. The bolt's rearward motionextracts the empty cartridge case from the chamber, and as soon as theneck of the case clears the barrel extension, the bolt's spring-loadedejector forces it out the ejection port in the side of the upperreceiver. The bolt is much heavier than the projectile, and along withthe recoil-spring pressure inside the stock buffer-tube performs thecartridge ejection function and chambers the following cartridge.

Behind the bolt carrier is a plastic or metal buffer which rests in linewith a bolt return spring that pushes the bolt carrier back toward thechamber to return the bolt into battery. A groove machined into theupper receiver traps the cam pin and prevents it and the bolt fromrotating into a closed position. The bolt's locking lugs then push afresh round from the magazine which is guided by feed ramps into thechamber. As the bolt's locking lugs move past the barrel extension, thecam pin is allowed to twist into a pocket milled into the upperreceiver. This twisting action follows the groove cut into the carrierand forces the bolt to twist and “lock” into the barrel's uniqueextension.

“Bolt bounce” is an undesirable phenomena associated with self-loadingfirearms, particularly fully automatic firearms. Specifically, when thebolt carrier comes forward and impacts the barrel extension, thepotential exists for the bolt carrier to recoil slightly. This can havethe undesirable effect of unlocking the bolt to a sufficient degree thatthe firearm is prevented from firing if the hammer falls again while thebolt is unlocked. Alternatively, if the bolt carrier is positionedexcessively rearward when the hammer strikes the retracted firing pinduring fully automatic fire, a misfire can occur because the boltcarrier absorbs energy from the hammer, thereby causing a too lightstrike by the hammer upon the firing pin.

Various solutions to the problem of bolt bounce exist, including thepreviously mentioned conventional buffered spring assemblies. Some ofthese have sliding weights inside the buffer portion, such as the bufferdisclosed in U.S. Pat. No. 8,800,424, which is hereby incorporated byreference in its entirety. When the mass of the sliding weights isresonant with the rebound of the bolt carrier as it contacts the barrelextension, the forces will cancel each other, thereby keeping the boltcarrier against the barrel extension in the desired in battery position.However, some firearms cannot accommodate buffered spring assemblies inthe stock, such as for pistol configurations. Furthermore, aconventional buffered spring assembly may be suitable for use with anunsuppressed fully automatic rifle using one kind of ammunition, but mayhave insufficient mass to adequately buffer the same rifle when asuppressor is used because of the greatly increased back pressureresulting from the suppressor, or when a different kind of ammunition isused. Overly energetic movement of the bolt carrier cannot only resultin bolt bounce, but can also result in potentially excessive wear andtear on rifle components.

Therefore, a need exists for a new and improved firearm bolt assemblyfor a self-loading firearm that has a tunable bolt carrier mass thatprevents bolt bounce. In this regard, the various embodiments of thepresent invention substantially fulfill at least some of these needs. Inthis respect, the firearm bolt assembly for a self-loading firearmaccording to the present invention substantially departs from theconventional concepts and designs of the prior art, and in doing soprovides an apparatus primarily developed for the purpose of preventingbolt bounce.

SUMMARY OF THE INVENTION

The present invention provides an improved firearm bolt assembly for aself-loading firearm, and overcomes the above-mentioned disadvantagesand drawbacks of the prior art. As such, the general purpose of thepresent invention, which will be described subsequently in greaterdetail, is to provide an improved firearm bolt assembly for aself-loading firearm that has all the advantages of the prior artmentioned above.

To attain this, the preferred embodiment of the present inventionessentially comprises an elongated frame defining a frame axis, a boltconnected to a forward end of the frame, a plurality of separate weightsconnected to the frame, and the weights being movable at least slightlywith respect to the frame and to each other for movement along the axis.There may be a resilient spacer element between adjacent weights. Theremay be a resilient spacer element between one of the weights and aportion of the frame. The spacer element may be an O-ring. The weightsmay be connected to a rear portion of the frame. The weights may betubular bodies each defining a bore. A portion of the frame may bereceived within the bore. The frame may define a rear portion having afirst diameter, and a flange forward of the rear portion having a seconddiameter larger than the first diameter. There are, of course,additional features of the invention that will be described hereinafterand which will form the subject matter of the claims attached.

There has thus been outlined, rather broadly, the more importantfeatures of the invention in order that the detailed description thereofthat follows may be better understood and in order that the presentcontribution to the art may be better appreciated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a right side view of the current embodiment of the firearmbolt assembly for a self-loading firearm installed in a firearm.

FIG. 2 is a front isometric view of the current embodiment of thefirearm bolt assembly for a self-loading firearm constructed inaccordance with the principles of the present invention.

FIG. 3 is an exploded view of the firearm bolt assembly for aself-loading firearm of FIG. 2.

FIG. 4 is a right side view of the firearm bolt assembly for aself-loading firearm of FIG. 2.

FIG. 5 is a bottom sectional view of the firearm bolt assembly for aself-loading firearm of FIG. 2.

The same reference numerals refer to the same parts throughout thevarious figures.

DESCRIPTION OF THE CURRENT EMBODIMENT

An embodiment of the firearm bolt assembly for a self-loading firearm ofthe present invention is shown and generally designated by the referencenumeral 10.

FIG. 1 illustrates the improved firearm bolt assembly for a self-loadingfirearm 10 of the present invention. More particularly, the firearm boltassembly is shown installed in a firearm 100. The firearm has an upperreceiver 102, lower receiver 104, barrel 106, suppressor 108, pistolgrip 110, trigger 112, magazine 114, and buttstock 116. In the currentembodiment, the firearm is an auto-loading rifle.

FIGS. 2-5 illustrate the improved firearm bolt assembly for aself-loading firearm 10 of the present invention. More particularly, thefirearm bolt assembly has a bolt carrier frame 12 having a right side14, left side 16, front face 18, rear portion 20, top 22, and bottom 24.The frame defines a longitudinal frame axis 26, and the front facedefines a central bore 28. The top front of the frame defines a charginghandle engagement shelf 30. A cam slot 32 is defined by the top of theframe immediately behind the charging handle engagement shelf. A carrierkey attachment area 34 is machined in the top of the frame directlybehind the cam slot. A plurality of forward assist notches 36 aremachined in the right side of the frame immediately behind the carrierkey attachment area. A hammer clearance slot 38, which communicates withthe central bore 28 is machined in the top of the frame immediatelybehind the carrier key attachment area. A flange 40 integral to theframe having a rear face 76 is located immediately behind the hammerclearance slot and forward assist notches. A rear portion 20 extendsrearwardly from the rear face of the flange to the rear 78 of the frame.A small turned groove 42 is present adjacent to the rear of the frame.

A stack of cylindrical, tubular weights 46, 56, 66 separated byresilient spacer elements in the form of elastomeric O-rings 44, 54, 64is received on the rear portion 20. The front weight 46 has a front 48,rear 50, and central bore 52. The intermediate weight 56 has a front 58,rear 60, and central bore 62. The rear weight 66 has a front 68, rear70, and central bore 72. The central bores of the weights aresufficiently larger than the outer diameter of the rear portion 20 ofthe frame 12 to enable the weights to be slidably received on the rearportion. O-ring 44 separates the front of the front weight from the rearface 76 of the flange 40 of the frame. O-ring 54 separates the rear ofthe front weight from the front of the intermediate weight. O-ring 64separates the rear of the intermediate weight from the front of the rearweight. A retention fastener 74, which is a spiral ring made of springsteel in the current embodiment, is snapped into the groove 42 to holdthe stack of cylindrical weights and O-rings on the rear portion of theframe. The weights are stacked tightly, but the compressibility of theO-rings means the weights are free to slightly reciprocate along therear portion of the frame. This movement of the weights provide somedamping, like a dead-blow hammer, and helps to absorb some energy in themanner of a buffer.

The weights 46, 56, 66 may be made of different materials havingdifferent densities, so that the user or assembler may choose from arange of selected bolt carrier masses determined by the particularweights attached to the bolt carrier frame 12. These metals may includestainless steel and tungsten, as well as other materials includinglighter materials such as aluminum or non-metal materials. The boltcarrier frame and weights may be supplied as a kit, with potentiallymore weights in the kit than can be installed, such as three each ofstainless steel and tungsten, with the user or assembler selecting whatcombination of different metals to use.

In the preferred embodiment, the mass of a stainless steel weight is0.58 oz., and the mass of a tungsten weight is 1.36 oz. Therefore, thetotal mass of the bolt carrier may be varied in steps equal to thedifference “D” between the stainless steel and tungsten weights, withthe total range of selectable weights being equal to 3×D. The factor of3 may of course vary based on the number of weights for which length onthe rear portion 20 of the frame is provided. The weights may each havethe same length, even when being made of different materials.

The need to change the bolt carrier frame mass (or to provide a customselected mass) may be based on many factors, including the type ofammunition used, whether or not a suppressor is used, whether firing isfully automatic or semi-automatic, and the type of shooting to beperformed. The buffering effect of the rubber O-rings and the ability totune the mass of the bolt carrier frame so the bolt fully cycles butdoes not move overly energetically is believed to reduce “bolt bounce,”especially from fully automatic, suppressed firearm operation, that cancause firearm malfunctions, as well as potentially excessive wear andtear on rifle components.

In the context of the specification, the terms “rear” and “rearward,”and “front” and “forward” have the following definitions: “rear” or“rearward” means in the direction away from the muzzle of the firearmwhile “front” or “forward” means it is in the direction towards themuzzle of the firearm.

While a current embodiment of a firearm bolt assembly for a self-loadingfirearm has been described in detail, it should be apparent thatmodifications and variations thereto are possible, all of which fallwithin the true spirit and scope of the invention. With respect to theabove description then, it is to be realized that the optimumdimensional relationships for the parts of the invention, to includevariations in size, materials, shape, form, function and manner ofoperation, assembly and use, are deemed readily apparent and obvious toone skilled in the art, and all equivalent relationships to thoseillustrated in the drawings and described in the specification areintended to be encompassed by the present invention. For example,although a gas impingement mechanism of operation has been disclosed,piston or blowback-operated mechanisms of operation could also be used.

Therefore, the foregoing is considered as illustrative only of theprinciples of the invention. Further, since numerous modifications andchanges will readily occur to those skilled in the art, it is notdesired to limit the invention to the exact construction and operationshown and described, and accordingly, all suitable modifications andequivalents may be resorted to, falling within the scope of theinvention.

1. A firearm bolt assembly for a self-loading firearm comprising: anelongated bolt carrier frame defining a frame axis; a forward end of theframe being adapted to receive a bolt; a plurality of separate weightsconnected to the frame; a toroidal elastomeric ring positioned betweeneach of the weights; and the weights being movable at least slightlywith respect to the frame and to each other for movement along the axis.